Translating mechanism for printing telegraph



TRANSLATING MECHANISM FOR PR'INTING TELEGRAPH Filed Feb. 2l, 1945 www -FLBPXCZ A l @MMM I-/w Dec. 31,1946'. J, T, GlLFlLLAN, JR 2,413,557

TRANSLATING MECHANISM FOR PRINTING TELEGRAPH Filed Feb. 21, 1945 2 Sheets-Sheet@ Jolzzz @10222.25 Gil/27]@ @om Q w New OON Patented Dec. 31, 1946 UNITED STATES PATENT OFFICE TRANSLATING MECHNSM FR PRINTING TELEGRAIH .lohn rlllriomas Giliillan, Jr., Kenosha, Wis.

Application February 2l, 1945, Serial No. 579,006

- Claims. 1

It is an object of this invention to provide a device capable of receiving manually transmitted telegrap'nic code symbols and translating each symbol into the typewritten letter or number which the symbol represents,

The above and other objects will be made clear from the following detailed description taken in connection with the annexed drawings in which:

Figure l is a diagram showing the apparatus as a whole;

Fig. 2 is a detail of the permutation bar restoring means;

Fig. 3 is a side elevation of the rotary switch advancing means; and

Fig. 4 is an end elevation of the parts shown in Fig. 3.

The prior art aords many examples of the combination of automatic transmission mth automatic reception but in all such installations a synchronizing medium is provided so that transmission and reception are at all times positively maintained in phase. Automatic transmission, however, makes it essential that a given message be manually transcribed upon a transmitting medium so that the transmitting medium may synchronize the transcribed message with the phase requirements of the receiver. For many purposes, especially in military requirements, this necessity oi' transcription at the point of origin is a serious difficulty; first, because of the time which must elapse between transcription and transmission; and second, because of the weight and bulk of the apparatus for transcription and transmission.

This invention contemplates the automatic reception and simultaneous printed transcription of messages manually transmitted by means of the usual key The invention is based on the fact that as the skill of the operato-r in the use of a telegraphic transmission lrey increases, all individual operators tend to approach a uniform plateau of speed, at which speed the following time factors tend to become uniform.

These are:

. The length of a dot;

. The length of a dash;

. The interval between consecutive dots and/or dashes;

fl. The interval between consecutive letters; and 5'. The interval between the end oi a word or sentence, and the beginning of the next word.

Eetween maxi-mum skill and what may be designated as an acceptable degree of proficiency, there may be a substantial range of overall speed oi transmission. lt will be found, however, that this increase of speed is, attained to a far greater extent by shortening the interval between consecutive letters and consecutive words, rather than by shortening the interval between dots and/or dashes, or the interval occupied by the individual dot or dash itself.

In terms of absolute time, it is clear that the incremental dirlerence between the length of a dot transmitted by an operator of merely acceptable pro-ciency and the length of a dot transmitted by the most skilled operator, is infinitesimal. While the total duration of a dash is considerably greater than that of a dot, and, accordingly, the absolute time increment represented by a percentage difference is greater, it must be remembered that the actual formation of a dot impulse or a dash impulse represents purely the functioning of a conditioned reex and at the level designated as acceptable proliciency such conditioned reflex is wholly divorced from conscious intelligence and, therefore, any difference in the duration of dot or dash impulses represent diilerences in the physical coordination ci the individual operator and not to any great extent the amount or degree of their training. It is, therefore, safe to assume that variations between a number of operators, all skilled at or above the level of acceptable proficiency, will be so slight that in terms of absolute increments of time, differences in the duration of dots and in the duration of dashes will be negligible.

The interval between dots and/or dashes in the formation of the symbol of a, single letter will be subject to slightly greater percentage variations between acceptable proficiency and maximum skill. This is because at the level of acceptable proiiciency there may still be involved an eiiort of the conscious intelligence in translating the letters of the message into code symbols. This conscious eiort tends to be replaced by conditioned reflex as the level of skill appreaches maximiun. As will appear hereinafter, however, the present apparatus requires less sensitivity in order to act on the interval between dots and dashes than it does on the duration of the dots and dashes themselves.

Obviously, the selection of letters of the message will always involve a considerable degree of conscious intelligence far less subject to replacement by conditioned reflex. The present apparatus, however. requires relatively little sensitivity with respect to pauses between letters, and still less as to pauses between words.

In the light of the foregoing, the principle upon which this apparatus is based may be summarized as follows:

First, as between individual operators, variations in the duration of individual dots and dashes will be at a minimum;

Second, maximum variations between individual operators will be encountered in the duration of intervals between letters and words;

Third, sensing devices must be provided, which devices will be responsive- (A) To the duration of individual dots and dashes;

(B) To the duration of the interval between letters; and

(C) To the duration of the interval between words.

The sensitivity of these sensing devices is adjusted to allow for the difference in the percent of variations which may occur in each of the three classes of intervals.

Before entering upon a detailed description of the apparatus, it is necessary to point out that all of the letters and numerals used in the International radio code are made up of from one to five dotand/or dash symbols, Grouping these, we nd that only two letters, E and T, comprise a single symbol-these being respectively, a dot and a dash. Only four letters comprise two symbols-these are A, I, M and N. Only eight letters comprise three symbols-these are D, G, K, O, R, S, U and W. There are twelve letters comprised of four symbols--these letters are B, C, F, I-I, J, L, P, Q, V, X, Y and Z. The ten digits, plus the symbol AR (meaning the end of a message), and BT (meaning a break in transmission), each comprise iive symbols.

In Figure 1, parallel connections are provided for each letter or numeral within each group and are respectively indicated by I through V. Each group is in parallel with a solenoid designated respectively I-5. These several solenoids are themselves in parallel to a common return lead I il which is connected to the key circuit by a lead lil. The solenoids I- are connected with the parallel groups I-V by means of leads 5', 2', 3', 4 and 5 respectively. The leads I through 5 are connected to contacts II, I2, I3, I4 and I5, respectively. A rotatably mounted disc 22 has formed in its perimeter a series of ratchet teeth II', I2', I3', I4 and I5. Aiiixed to the disc 22 is a movable contact arm 24 which is electrically grounded at 26. A pawl 28 is mounted on one end of a lever 3! which rests on a fulcrum 32 and is biased by a spring 34 to hold the pawl 28 in upward position. The lever 30 constitutes the armature of a solenoid H, and whenever the solenoid H is energized, the lever 39 and pawl 28 are drawn downwardly thereby advancing the rotating contact 24 `by onenotch. Solenoid H is grounded at 2!) and connected to key circuit in parallel with solenoids I-5 by lead III. It is clear, therefore, that upon each closure of the key K the solenoid H will be energized.

When the key circuit opens at the end of each dot or dash,the solenoid I-I will be deenergized, releasing the lever 3E) which will swing about the fulcrum 32 under the pull of spring 34, thereby advancing the pawl 23 to the next ratchet tooth thereabove. The disc V2 is connected with a torsion spring 38 (Fig. 3) which tends to move the disc counter-clockwise and thus always to return it to starting position. A supplemental pawl 48 isv pivoted at 42 and is impelled by a spring 44 to engage the ratchet teeth I I through I 5. The pawl 40 operates as a lock to prevent return of the disc 22 during the return movement of the pawl 28.

A'series of permutation bars I through 5" are provided corresponding respectively to solenoids i-5. Each or" the permutationbars I" through 5" is slidable and bears a series of conductors extending transversely thereof. By means presently to bedescribed, all lof the bars at the beginning of the transmission of each letter are biased to the left in the position shown in Fig. l

and the conductors on each bar are so arranged that those contacts which are required to be operative for the transmission of a dot are in operative position when the bars are in the position shown in Fig. 1. If any of solenoids I-5 be energized, its permutation bar will be withdrawn to the right of the position shown in Fig. 1 and its contacts will then be in dash transmitting position. A side bar 56 is provided as a guide for permutation bar I and at the opposite side ofthe system a guide bar 6G is in sliding contact with permutation bar 5". Bars 50 and G have a number of conductors extending transversely thereof. Each conductor corresponds to a letter or digit. Contacts of the bar 5I) are individually connected to the parallel leads of groups I through V. The contacts of the bar 60 are each connected to a solenoid 62 and each solenoid operates or brings about the operation of a type bar or other suitable typing or printing means corresponding to a particular letter or digit. All of the solenoids 62 are connected in parallel through lead 64 which is connected to contact I6 of relay B.

When the leads of group I are grounded at 26.

through contact II and arm 24 and the bars I5" are in the position shown in Fig. 1, the solenoid 62 corresponding to the letter E will be ready to be energized to type the letter. If, however, permutation bar I were moved to the right, to its dash position, and group I were grounded, the solenoid 62 corresponding to the letter T would be made ready to be energized to type that letter. This is interpolated here in order to provide a clarifying example of the functioning of the transverse conductors on the permutation bars. It is now necessary to describe the sensing devices which serve to differentiate between dots and dashes, the intervals between letters, and the intervals between words.

The sensing devices comprise relays B, C, and D. Relay B is made up of a solenoid 'I0 grounded at 12, a movable armature 74, and a contact 1E. The armature 14 is biased so as normally to encounter the contact 78. Relay C is made up of a solenoid 8B grounded at 82 and having an armature 84 and a contact 88. The armature 84 is normally biased to encounter the contact 8B. Relay D is made up of a solenoid 90 grounded at S2 and having an armature 94 and a contact 96. The armature 94 is biased so as normally to encounter contact 96. Solenoids 1U, 88 and 90 are in parallel, through a lead IUI), with the key K and also with the disc actuating solenoid H. The armatures 14, 84 and 94 are in parallel through a lead IIlZ with the opposite side of the key K. It is to be noted that the lead |82 connects to the positive side of the battery or other source of potential IIN. Each of the relays B, C and D is of the time delay type in which the armature will be drawn away from the contact instantly upon the solenoid being energized but a predetermined interval of time will elapse after the solenoid is de-energized and before the armature returns to contact making position. When the key K is closed, current flows from the battery |04 through the key, through lead I 00 and simultaneously energizes solenoids 10, and 90, thereby simultaneously drawing armaturesy 14, 84 and 94 away from their respective contacts. So long as the key is held down, the armatures 14, 84 and 94 will continue to be held out of contact making position. lTherefore, whether the key be held down long enough to form a dot or to form a dash, is immaterial, since contacts 16, 85 and 96 must in all events remain open.

It will be noted that solenoid H is in parallel with relays B, C and D, and, therefore, is energized simultaneously with .said relays when the key is closed. Therefore, instantly upon closing of the key circuit, disc 22 and contact 24 are rotated one notch. With the parts in the position of Fig. 1, closure of the key will open relays B, C and D, and will' advance contact 24 from position l! to position il. rIhis will ground solenoid i (on permutation bar l) through the lead Il, but solenoid i through lead l and closed key K is at the same time connected to the positive side of battery i. Solenoids 1 5 are proportioned and designed relative to the effort necessary to move the permutation bars so that unless the key K remains closed for the duration of a dash, solencids l-5 will not act to withdraw their respective permutation lbars to dash position. Transmission of a dot, therefore, will merely advance the rotating contact 2li without `moving the permutation bars from their normal dot position.

The letter E is represented in the code by a single dot. As the key is depressed, relays B, C and D are opened; relay H advances contact 24 so as to connect contact il to ground 2t; solenoid i is momentarily energized but insui'liciently so to eiiect the position of permutation bay l". The solenoid 62 corresponding to the letter E is grounded via the conductors extending across bar t0, permutation bars I"5", bar 5u, contact ll, and ground 2t. Lead 54 which is in parallel with all of the printing solenoids is connected to contact 'iii of relay B. At the conclusion of the dot, there will be a distinct pause before the beginning of the next letter. During this pause, solenoid l0 or relay B is de-energized and the armature 'M goes back to encounter contact 16 and complete the circuit of letter E through lead m2 to the positive side of battery i042. Since E is a letter in itself, there will be a longer pause before the key is closed again than would be the case in forming the consecutive dots and dashes of a single letter before the key circuit is again closed. During this additional pause and while solenoid Sil of relay C is cle-energized, its armature fili, shortly after the closing of armature 'it of relay B, makes contact with 36 and, through lead i612 and an additionaly lead I EG, energizes a solenoid E which is grounded at H4. This solenoid, by means described in detail hereafter, actuates a restoring bar H6 which on its downward movement tends to move all the permutation bars to dot position. In the example just considered, this is without effect because no bar is in dash position when the letter E is transmitted.

It is to be noted that a solenoid F is in parallel with the solenoid E and is grounded at IRQ. Solenoid F is arranged to rock pawls 28 and 40 out of engagement with the teeth of disc 22, and torsion spring 38 then returns the rotating contact 24 to the il position shown in Fig. l.

It E happens to be the end of a word, there will be a still longer pause before the key K is again closed. During this longer pause, solenoid Sill of relay D is dewenergized and its armature @4 returns to meet its contact 95 and thus to enn ergize a solenoid G grounded at dii. Solenoid G operates the spacer of the typing mechanism and, therefore, enters the proper spacing between words.

The operation of the apparatus in receiving the letter X will now be considered as being a more comprehensive example than the letter E. The symbol for X is With the parts of the position shown in Fig. l., key K is closed and maintained closed for the duration of a dash. The closure of the key immediately opens relays B, C and D, energizes solenoid H, and advances rotating contact 24 to position ii. The duration 0f a dash is sufficiently long to energize solenoid l to the extent of enabling it to withdraw permutation bar i from the position shown in Fig. l to its alternative rightward position. A stop member l5ll is provided to limit the movement of the permutation bars under the eiect of their respective solenoids. At the conclusion of the dash the key opens and in the very brief pause before the beginning of the next symbol there is not time enough for relays B, C and D to close their respective circuits. Two dots are then transmitted by the key. Closure of the key re-energizes solenoids l0, 8G and 9! of relays B, C and D and thereby provides a new starting point for their time delay intervals. Each dot, by means of solenoid H, advances Contact 25 from position ii to position I2 and then from i2 t0 i3. Each dot, therefore, momentarily closes the circuit of solenoids 2 and 3 respectively, but are of such short duration as not to alter the leftward, or dot, position of permutation bars 2 and 3". To complete the transmission of the letter X a dash is now struck on the key. This advances the rotating contact 2li to position it closing the circuit of solenoid #i and, since it is a dash, maintaining the circuit closed long enough to draw permutation bar Li" to the right, or dash, position. rhere is now a substantial pause before the transmission of the next letter. During this pause, armature i4 of relay B encounters contact 'it to energize the solenoid 62 corresponding to the letter X and thereby to type the letter. Au instant after X has been typed, armature 8C. of relay C encounters Contact 86 and ysirmiltameously energizes solenoid E to restore permutation bar I" and 4 to their original or dot position, and solenoid F to withdraw pawls 2S and and to permit disc 22, under the eect or torsion spring 38. to restore rotatingcontact 24 to 0 position. If the pause following transmission of the last dash in the letter X is only long enough to form a proper pause between letters, the key will be closed again before armature 94 of relay D can encounter contact QS. Only a pause long enough to indicate the break between words will permit the circuit of relay D to' be closed.

It is to be noted that this apparatus will function eectively only if the transmitting operator is skilled above a certain minimum level of proficiency. Above such level, the pauses between letters becomes quite uniform as between various operators, as do the pauses between words. and the difference in duration of the two types or" pauses also becomes uniform. It does not matter how short the interval between consecu tive dots and/or dashes. It would, however, disn rupt operations i the pauses between consecutive dots and/ or dashes should become suiiciently long to permit operation of any of the relays B, C and D. Fortunately, it is the interval between consecutive dots and dashes which tends to shorten more abruptly as the proficiency or the operator rises from the level of merely acceptable operation to the level of expert operation.

It will be understood from the foregoing that the operation of relays B, C and D is completely unalected by variationsin the duration of the impulseof individual dots and dashes. These relays can only be affected by the duration of the intervals during which the key circuit is open.

It is necessary that relay B shall resume closed circuit condition within the interval between consecutive dots and/or dashes. Assuming a minimum level of acceptable prociency in the skill of the operator, there should never be any confusion between such intervals, and the solenoid B need only be designed for a time delay in closing the circuit upon being de-energized, which time delay will substantiallyexceed the average interval between individual dots and dashes, and which will be substantially shorter than the average interval Abetween consecutive letters. rFhis is an operation so far within the range of measurable time as -not to impose an undue burden of design in the actual layout of relay B. The absolute time interval between letters is from two to live times the absolute time interval between individual dots and dashes (always assuming a reasonable minimum level of skill on the part of the operator), and since the interval between letters is distinctly measurable, it is relatively easy to time the action of relay B so as to fall short of the minimum interval between letters, while being distinctly greater than the maximum interval between individual dots and dashes.

Of the three relays B, C and D, relay B presents the most severe requirement of sensitivity. Relay C must be responsivein general to the same intervals as relay B, but must always in its delaying action occupy a iinite rincrement of time in addition to the time occupied by the delaying action of relay B. This, for the reason that the action of relay B in energizing the solenoid corresponding to a particular printed letter must be complete before relay C can be permitted to close the circuit of solenoid E. i

Relay D need be responsive only to the relativelylong interval occurring between words. It must not close at the interval between consecutive dots and/or dashes, and it must lnot close during the interval between letters. The interval between letters is, of course, shorter than the interval between words, but as previously discussed, the range of variations as between individual operators will be greater than such range of variation in the other interval.

The basic requirement is that relay D must never clo-se until after relay C has closed, but it must close before the key is again operated in order to provide word spacing in the typewritten message.

The relayY I-l must perform a severe mechanical job in advancing the point contact A,`and must accomplish -this advance within the absolute minimum of time in which its circuit is energized by the key making contact. That is, the pointer must advance, for example, from zero to 1, under the influence of relay H, and thereby energize solenoid i ,to withdraw its permutation bar from dot to dash position in the duration of a single dash. Solenoid I must not, however, move its permutation bar in the duration of a single dot Vsince this would disturb the basisof permutation.

Sensitivity of relay I-I and solenoids i-i must, tbereforebe such that solenoid H will function. to advance the pointer on an interval of a single dot, and the time consumed by the advance of the pointer must be such that not enough time remains Vto energize solenoids l-5, unless the symbol is a dash. In the case of a dash, the key remains closed long enough after the pointer arrives at a station to permit the requisite solenoid (i-E) to be energized.

Fig. 2 is an enlarged view illustrating the mechanism by which relay E is enabled t0 restore the permutation bars from dash to dot position. The rod i iii is biased by a spring 20B toward the position illustrated in Fig. 1 and is drawn downwardly by solenoid E when the solenoid i-s energized. The rod H6 has a wedge HEY formed on' one side for each permutation bar. -In Fig. 2 the permutation Ibar l is illustrated as `having a bellcrank 292 pivoted to its leftward extremity by means of a pivot 204. One arm 266 of the bell crank 2%2 has at its extremity a roller 208 adapted to contact the inclined surface of the wedge HS. The arm 286 rests against a stop or abutment 2i!) formed in the permutation bar I. The opposite arm 242 of the bell crank 202 has a spring It joining its extremity to the abutment 2id so as to bias the arm 2% against said abutment. When the rod IIB under the pull of solenoid E is drawn in the direction of the arrow, the inclined surface of wedge IIS engages the roller 298, and since the abutment ZID prevents the arm 26E from swinging about the pivot 204, the wedge H6' forces the permutation bar l to the left. The rod H6 is drawn down by the solenoid E until the upper edge H6 of the Wedge.

H clears the roller 208.,

Relay E can be energized only when armature 8:3 of relay C encounters its Contact 86, but once the key K is in open position and armaturetll makes the circuit with contact 86, solenoid E will remain energized and the rod HS will, therefore, remain in downward position until relieved as hereinafter set forth.

It will be noted that the circuits controlled by the armatures and contacts of relays B, C and D will remain closed, so far as these relays are concerned, for so long as the device is not in operation. At the same time it i-s desirable that the device be at all times ready for operation since, particularly for military use, messages may arrive at any unpredictable time. In order to avoid a power drainage upon a limited source of power such as a battery, it is desirable to limit theamount of current drawn through the relay circuits and in particular with respect to solenoid F, it is desirable that this solenoid be de-energized before the start of a message so that the pawls 28 and d@ will be in their active position ready to function within the extremely small time in'- terval occupied by the reception of a dot. In the case of a relay F, this is accomplished by inserting in its lead line 582 a relay L comprising an armature 33t drawn by a spring 392 toward circuit closing position and having a coil 301i, one end of which is connected at 396 to the lead |02' intermediate the relay L and the relay C. The other end of the coil 304 is grounded at 398. Relay L is a time delay relay opposite in phase to the type of time delay provided in relays C and D, that is, it will not function to open the circuit through relay E' until current has ilowed through the coil 3M for a perceptible time. The coil 3M is designed for extremely high resistance so as to .minimize the current flowing therethrough. W en the relay D is open, the circuit of coil it isV broken and the spring 3632 draws the armature Se@ to a position where it completes the circuit of solenoid F. This will be the condition of things so long as relay D is open.- When relay D closes, armature 30G at rst remains in circuit closing position, but if relay D remains closed more thana short interval, coil 30d which is energized instantly on the closing oi relay D will operate to withdraw the armature 3%?) and thereby to de-energiae solenoid F, permitting pawls 2S and lil to return to active position and relay L will therefore remain energized until relay D is again open. A similar' relay M is provided in the line i9 going to solenoid E, a similar relay N is provided in the lead l lil going t solenoid G, and a similar relay P is provided in the line of solenoid B.

When the typing machine is designed to operate on a continuous tape, there is no opportunity to rewind a carriage feeding spring and, therefore, the spacing is preferably accomplished electrically.` For such an installation, an additional coil G', grounded at Sii is wound on the armature of the spacing relay G and is connected by a lead 64 to the lead 6G.. This means that the spacing relay G is operated upon the typing of each letter, as well as by relay D upon the conclusion of a word.

While a key has been shown for initiating the dot and dash impulses, it is clear that any other source could be used. The impulses, for example, may be amplified radio signals. The apparatus is designed only to translate groups of consecutive impulses into the various letters, numerals and symbols represented by each group of impulses. The precise printing mechanism is, therefore, irrelevant and is not here disclosed.

I claim:

1. In a telegraph printing apparatus, a plui rality of type-bar operating elements, a series of permutation bars bearing mutually engageable contacts and arranged for sliding movement relative to one another between two positions, fixed contact means mounted alongside an end bar of said series and having a plurality of contacts each connected to one of said operating elements, second xed Contact means mounted alongside the other end bar of said series and having a plurality of contacts connected in parallel groups, multicontact selector mechanism, each of Said groups being connected to one contact of said selector mechanism, means responsive to the duration of individual impulses of a code series for controlling the positioning of said permutation bars, means responsive to the number of impulses in a code series for controlling the operation of said selector mechanism, and a return circuit connected to a. source of power, to said selector mechanism and to all of said operating elements.

2. In a telegraph printing apparatus, a plurality of type-bar operating elements, a series of permutation bars bearing mutually engageable contacts and arranged for sliding movement relative to one another between two positions, xed contact means -mounted alongside an end bar osaid series and having a. plurality of contacts each connected to one of said operating elements, second fixed contact means mounted alongside the other end bar of said series and having a plurality of contacts connected in parallel groups, multi-contact selector mechanism, each of said groups being connected to one contact of said selector mechanism, means responsive to the duration of individual impulses of a code series for controlling the positioning of said permutation bars, means responsive to the number of impulses in a code series for controlling the operation of said selector mechanism, a return -circuit connected to a source of power, to said selector mechanism and to all of said operating elements, and means normally interrupting said return circuit and responsive to the duration between successive series of impulses for closing said circuit in response to the absence of an impulse for a predetermined time.

3. In a telegraph printer apparatus, a plurality of operating elements for character printers, a circuit connector mechanism, means connecting each ci said operating elements to said connector mechanism for selective energization thereof, a selector mechanism movable in one direction for sequentially connecting groups of operating elements to a source of current, means responsive to the duration of a code impulse for controlling said connector mechanism, means responsive to the number of impulses in a code series for advancing said selector mechanism stepwise in one direction, and means responsive to the duration between series of code impulses for completing a circuit from said current source through said selector mechanism, said connector mechanism and one of said operating elements, and means responsive to the absence of an impulse for a predetermined time for rapidly returning said selectoi mechanism to its original position in the opposite direction.

4. In a telegraph printer apparatus, a plurality of operating elements for character printers, a common return circuit permanently connected to all of said operating elements, a circuit connector mechanism, means connecting each or said operating elements to said connector mechanism for selective energization thereof, a selector mechanism for sequentially connecting groups of operating elements to a source of current, means responsive to the duration of a code impulse for controlling said connector mechanism, means responsive to the number of impulses in a code series for controlling said selector mechanism, and means responsive to the duration between series of code impulses for completing a circuit from said current sc-urce through one of said operating elements, and for rapidly restoring said selector mechanism with a minimum of delay to its condition prior to the beginning of the said series of pulses.

5. In a telegraph printer apparatus, a plurality of groups of operating elements for character printers, a common return circuit permanently connected to all of said operating elements, connector means responsive to the length of each of a series of impulses for connecting one element only of each group to a respective circuit, a springreturned multi-contact selector switch operable by each of said pulses for sequentially connecting said circuits to a source of power, and means responsive to the absence of an impulse for a predetermined time for completing a circuit from said power source to all of said operating elements and for restoring said connector means and said selector switch rapidly to their normal positions, said selector switch having a dead or non-contacting position to which it is operated by any surplus non-significant impulse in excess of the maximum number of impulses per series in the anticipated code, whereby such a surplus impulse is ineffective to cause a connection from any of said circuits to said power source.

JOHN THOMAS GILFILLAN, JR. 

